Examples of the placebo effect

One well-known example of the placebo effect involves a physical feeling we are all familiar with: pain.

In 1996, scientists assembled a group of students and told them that they were going to take part in a study of a new painkiller, called "trivaricaine".

Trivaricaine was a brown lotion to be painted on the skin, and that smelled like a medicine. But the students were not told that, in fact, trivaricaine contained only water, iodine and thyme oil – none of which are painkilling medicines. It was a fake – or placebo – painkiller.

With each student, the trivaricaine was painted on one index finger, and the other left untreated. In turn, each index finger was squeezed in a vice. The students reported significantly less pain in the treated finger, even though trivaricaine was a fake.

In this example, expectation and belief produced real results. The students expected the "medicine" to kill pain; and, sure enough, they experienced less pain. This is the placebo effect.

Placebo medicine has even been shown to cause stomach ulcers to heal faster than they otherwise would.

These amazing results show that the placebo effect is real, and powerful. They mean that fake or placebo treatments can cause real improvements in health conditions.

Experiencing the placebo effect is not the same as being "tricked", or being foolish. The effect can happen to everyone, however intelligent, and whether they know about the placebo effect or not.

CAM and the placebo effect

Evidence about a treatment is gathered by conducting fair tests. In these tests, scientists find out whether a treatment causes an improvement beyond the improvement caused by the placebo effect alone.

Evidence plays an important role in mainstream medicine. This means that when you use many conventional medicines, you can be sure there is evidence they work.

When patients experience improvement after using a healthcare treatment that has not been proven to work, they may only be experiencing the placebo effect.

Of course, improvement in a health condition due to the placebo effect is still improvement, and that is always welcome.

But it is important to remember that for many health conditions, there are treatments that work better than placebos. If you choose a treatment that only provides a placebo effect, you will miss out on the benefit that a better treatment would provide.

Checking the evidence for or against a treatment

The only way to know whether a health treatment works better than a placebo treatment is by checking the evidence.

You can read about the evidence for different CAMs on pages about specific treatments. See our index for a list of all treatments covered by NHS Choices.

How evidence is gathered and used

The best way to produce good evidence on a health treatment is to conduct a fair test. Here, the medicine or treatment being tested is compared to another treatment, or to a placebo.

Tests are made as fair as possible by minimising bias and the role of chance. This means that the test results will reflect, as far as possible, the truth about the medicine or treatment, and will not be influenced by other factors, such as the way the test was carried out, or the attitudes of the people who take part.

Scientists often call these fair tests clinical trials.

Before scientists conclude that a health treatment is safe and that it works, there must usually have been several independent tests of the treatment that have shown this.

Sometimes, different fair tests can give results that disagree.

The results of fair tests can provide:

results that show the medicine or treatment does work and is safe; this is often call positive evidence, or evidence for the treatment

results that show the medicine does not work, or is unsafe; this is often called negative evidence, or evidence against the treatment

Negative evidence – that is, evidence against a treatment – is not the same as no evidence. Negative evidence means a set of results showing that a medicine or treatment does not work.

No evidence simply means an absence of any evidence, because fair tests have not been conducted.

Where to find out more

Read about the evidence for different CAMs on pages about specific treatments. See our index for a list of all treatments covered by NHS Choices.